Traditionally artificial vision systems have been either discrete or continuous.
Discrete systems are characterized by a large number of logical states (0 or 1), normally implemented by a computer, which gives a rich structure. This allows for switching of the system between many different states implementing different models. However, a continuous transition between models is often difficult with such a structure, since the discrete switching structure can not easily transfer knowledge about system states and boundary conditions.
A continuous system implements classical control strategies. This generally allows only a fairly limited complexity, with a limited number of variables, since the systems otherwise become very unwieldy.